I recently built the Kog and used a few of the viking figures to give a sense of scale and thought they worked very well. They are slightly bendable so you can alter the oarsmen's positions slightly, although its best to do this before painting as the paint can flake when you start bending the figures, even when primed with a pva solution.
I also took a couple of the figures and tried wrapping some thinly pressed out clay around them to create a cloak which was easy to do and I thought quite effective.
Also I was in my local model shop last week and found a new Zveda kit, a Medieval Life Boat which is 1/72, is only 9.5cm long and is cheap. I'm not sure of the historical accuracy but I decided to add it to my Kog display using the viking oarsmen with it to create a basic diorama and think they should look well. I built my Kog in full sail and if I'd had the Life Boat beforehand I might have tried for a diorama with her in harbour instead. Maybe next time.